2027 ICD-10-CM Diagnosis Code Z23Encounter for immunization
Z23 is a billable ICD-10-CM diagnosis code for encounter for immunization. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 795, 951. The code is not accepted as a principal diagnosis by the Medicare Code Editor and exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Exposure, encounters, screening or contact with infectious disease.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for Z23.
Present on Admission (POA)Billing
Z23 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review the other POA exempt codes in Persons with potential health hazards related to communicable diseases (Z20-Z29).
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- 1st Hib and DTP vaccine given
- 2nd Hib and DTP vaccine given
- 3rd Hib and DTP vaccine given
- Administration of human papilloma virus type 6, 11, 16, and 18 vaccine done
- Bacillus Calmette-Guerin vaccination given
- Chikungunya virus vaccination given
- Cholera vaccination given
- Diphtheria and acellular pertussis and inactivated poliomyelitis and tetanus vaccination given
- Diphtheria and tetanus and acellular pertussis and Haemophilus influenzae type b and inactivated poliomyelitis vaccination given
- Diphtheria and tetanus and acellular pertussis and Hepatitis b and inactivated poliomyelitis vaccination given
- Diphtheria and tetanus vaccination given
- Diphtheria vaccination given
- Diphtheria, tetanus and acellular pertussis vaccination given
- Diphtheria, tetanus, pertussis and polio vaccination given
- Haemophilus influenza type B vaccination given
- Has influenza vaccination at home
- Has influenza vaccination at hospital
- Has influenza vaccination at surgery
- Has influenza vaccination at work
- Herpes zoster vaccination given
- Human papilloma virus type 16 and 18 vaccination given
- Human papilloma virus vaccination given
- Human papillomavirus 6, 11, 16, 18, 31, 33, 45, 52 and 58 vaccination given
- Influenza A H1N1 vaccination given
- Influenza vaccination given
- Influenza vaccination requested
- Influenza vaccination status
- Intranasal influenza vaccination given
- Measles vaccination given
- Measles vaccination requested
- Measles, mumps and rubella vaccination given
- Meningococcus vaccination given
- Mumps vaccination given
- Pneumococcal 13-valent conjugate vaccination given
- Pneumococcal 20-valent conjugate vaccination given
- Pneumococcal 23-valent polysaccharide vaccination given
- Pneumococcal 7-valent conjugate vaccination given
- Pneumococcal vaccination given
- Poliomyelitis vaccination given
- Procedure needed
- Rabies vaccination given
- Respiratory syncytial virus vaccination given
- Rotavirus vaccination given
- Rubella vaccination given
- Tetanus toxoid vaccination given
- Travel vaccination given
- Typhoid vaccination given
- Vaccination given
- Vaccination needed
- Varicella-zoster vaccination for chicken pox given
- Varicella-zoster vaccination given
- Viral hepatitis A and B vaccination given
- Viral hepatitis A vaccination given
- Viral hepatitis B vaccination given
- Yellow fever vaccination given
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to Z23: its own notes plus those printed at Chapter 21. A note printed at a category, block or chapter applies to every code under it.
Code First
The underlying condition named in the note is sequenced before this code.
- any routine childhood examination
Code Also
A second code may be needed to fully describe the condition; the note gives no sequencing direction.
- if applicable, encounter for immunization safety counseling (Z71.85)
Notes
General instructions on how these codes are used.
- procedure codes are required to identify the types of immunizations given
- Z codes represent reasons for encounters. A corresponding procedure code must accompany a Z code if a procedure is performed. Categories Z00-Z99 are provided for occasions when circumstances other than a disease, injury or external cause classifiable to categories A00-Y89 are recorded as 'diagnoses' or 'problems'. This can arise in two main ways:
- (a) When a person who may or may not be sick encounters the health services for some specific purpose, such as to receive limited care or service for a current condition, to donate an organ or tissue, to receive prophylactic vaccination (immunization), or to discuss a problem which is in itself not a disease or injury.
- (b) When some circumstance or problem is present which influences the person's health status but is not in itself a current illness or injury.
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name Z23, its category, or a range that includes it.
Code Also 2
These codes say Z23 may also be needed to fully describe the condition. The note gives no sequencing direction.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Admission (for) See Also: Encounter (for);
prophylactic (measure) See Also: Encounter, prophylactic measures;
vaccination Z23
Immunization See Also: Vaccination;
encounter for Z23
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Vaccines
Vaccines are injections (shots), liquids, pills, or nasal sprays that you take to teach your body's immune system to recognize and defend against harmful germs. For example, there are vaccines to protect against diseases caused by:
The full article covers:
- What are vaccines?
- What are the types of vaccines?
- What happens in an immune response?
- What are immunization and vaccination?
- Why are vaccines important?
- What is community immunity?
- Are vaccines safe?
- What is a vaccine schedule?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert Z23 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About Z23Overview
What is the ICD-10 code for encounter for immunization?
The ICD-10-CM code for encounter for immunization is Z23. It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is Z23 (Encounter for immunization) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report encounter for immunization on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does Z23 group to?
On inpatient claims, encounter for immunization maps to MS-DRG 951, 795, with relative weights from 0.2022 to 0.5574 depending on complications. Higher weights mean higher Medicare reimbursement.
Can Z23 be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because encounter for immunization describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
Is Z23 exempt from POA reporting?
Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for encounter for immunization on inpatient claims. The code appears in the Persons with potential health hazards related to communicable diseases (Z20-Z29) range of the CMS exempt list.
